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My rogue-like game is undergoing fundamental restructuring to allow all entities to be read in from XML files. I wouldn't call it a rewrite, really. Only the base classes have required refactoring, thanks to what I now feel is a pretty good OO design. Anyways, in the process of doing this, I had an excellent opprotunity to rework my MapCtrl, which is a component that attaches to a Map and renders it using Direct3D. I thought I would share my experience trying to get performant tilemap rendering out of DirectX in case anyone else was tempted to go this route now or in the future. DirectX is unweildy for making simple 2D games because DirectDraw has been deprecated - so to do anything graphical, you need to use Direct3D. Originally, I just wanted to get something working, so I was rendering my tilemap in a very straightforward way. I have a vertex buffer holding a quad that I would translate over the map, drawing one tile at a time. This gave me awful performance (1.5 FPS with a 100x100 fully in view). After much research, I learned that changing render states is very expensive in D3D. Specifically, set texture and DrawPrimitive calls. In order to get a fast tilemap in D3D, it is necessary to do the following: 1. Batch all your textures. To minimize texture changes, you need to put all your tiles onto one (or possibly several) larger textures. 2. Use dynamic vertex buffers to blast several thousand polies to the screen at once. For each tile you want to add, you append the geometry to the buffer and set the texture coordinates to corrospond to your batched tile. Using an index buffer is a good idea, you will use 33% less bandwidth piping geometry to the GPU. 3. When the dynamic buffer fills up, or you need to make a texture swap, write out the buffer with DrawIndexedPrimitives, and start to fill it up again. 4. Clearly you only do this for onscreen tiles. 5. If you have a ton of textures, you should sort your tiles to minimize texture swaps. This probably isn't an issue since even my Geforce 440 Go supports 2048x2048 textures and you can put a lot of tiles into a bitmap that large. I just got this working today, after fighting with DirectX for the past couple of days. I do get really good performance: 70 FPS rendering a 100x100 tilemap, fully in view (at arbitrary scale). But it took more effort than it should have. I needed this level of performance so that I can run animations at 30 FPS without needing dirty rectangle techniques and without driving my CPU to 100% (my computer sounds like a jet plane taking off when it gets going). But probably, if you will be much happier with OpenGL or SDL if you want to make a simple graphical tilemap. My 2c. --- PS - Thanks to Barakus and EDI for helping me fix the issues I was having with my tilemap.

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This is what I do in my 2D sidescroller too. The artist creates 256x256 textures, and the map editor uses these to paint tiles on the map. When the game loads the map, it gets a list of all the textures it needs, and works out the best size to use (512x512, 1024x1024, 2048x2048 or 4096x4096) based on the number of textures required, the amount of space that would be wasted, and the maxiumum texture size the card supports.
Example: One map requires 7 different 256x256 textures. That means that the game can chose to use a 1024x1024 texture, and waste 9 256x256 areas, or it can chose to use two 512x512 textures, and only wast 1 256x256 texture area.
Also note that most ATi cards only support up to 2048x2048, apart from the latest ones (X1xxx cards).

Another thing you could try doing (I don't, but I intend to) is if your visible map area is 30x20 or something, you can fill the VB with 32x22 tiles, and then just use the world matrix to translate the map. That means you only need to fill the vertex buffer when a new tile comes into view, which should give you a bit of performance.

Using index buffers is pointless for 2D tile engines, since each vertex is used exactly once (Due to texture coordinates being different where vertices could be shared). So you're just as well to render as much as possible (often the whole screen) in one DrawPrimitive() call.

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Quote:
Original post by Evil Steve
...
Using index buffers is pointless for 2D tile engines, since each vertex is used exactly once (Due to texture coordinates being different where vertices could be shared). So you're just as well to render as much as possible (often the whole screen) in one DrawPrimitive() call.

Actually, for each quad, you can cut the number of vertices down from 6 to 4, since the two triangles that make up the quad do indeed share two vertices, texture coordinates and all. (Thus Telamon's 33% less bandwidth figure.) I'm guessing you probably knew this, but just briefly forgot about it. But for anyone else's information...

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Yea, D3dX sprite functionality make 2d games an absolute breeze. Direct Draw is crap. They did good to abandon it.

An old game I did a few years ago in school was incredibly easy with d3dx sprite.

Game

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Original post by Telamon
DirectX is unweildy for making simple 2D games because DirectDraw has been deprecated - so to do anything graphical, you need to use Direct3D. Originally, I just wanted to get something working, so I was rendering my tilemap in a very straightforward way. I have a vertex buffer holding a quad that I would translate over the map, drawing one tile at a time. This gave me awful performance (1.5 FPS with a 100x100 fully in view).


I'm getting really tired of this "bring back DiriectDraw" crap. Direct3D isn't that hard, don't blame it because you couldn't research the proper way to do things. D3D can do ANYTHING DirectDraw can, some even FASTER than DirectDraw.

For my TileStudio loader and Snake.Net , I used the Managed Direct3D sprite class and the frame rate is fine even in debug mode.

I'm sorry if this post sounds mean, but I've gotten tired of having to defend D3D every few days. Don't bash an API you don't know how to use. I'm sure the OGL crowd wouldn't like it if I went in and said "OMG I can't draw 1000000000 quads at once, OGL SUCKS!!!!111!".

Edit: Thanks DrEvil.

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Telamon, there must be something else in your code that's straining DirectX: I can do 4 layers with tiles spanning two textures, using simple DrawPrimitiveUP (insert BOOs here), some alphablended and a background image without any framerate problems on a P3 800.

Do you cache your renderstate sets? Do you use several tiles on a single texture? Any reason you can't use pretransformed vertices?

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My 2-pence for what it's worth...

Quote:
DirectX is unweildy for making simple 2D games because DirectDraw has been deprecated
I'm with Scet on this one. I will concede that the initial learning curve (or is it a hurdle?) is steeper, but the rewards are awesome. My experiences in the good old-days were that you could get something simple up and running in DD7 very quickly but you could quite quickly hit it's limits. Once you'd hit the limits you either had to stop or invest a lot of time developing custom code and/or work-arounds. In the long-run Direct3D doesn't have this problem in my experience.

Quote:
I was rendering my tilemap in a very straightforward way. I have a vertex buffer holding a quad that I would translate over the map, drawing one tile at a time. This gave me awful performance (1.5 FPS with a 100x100 fully in view).
(emphasis mine) Does not surprise me in the slightest that you got crap performance this way [smile] 100x100 tiles would generate 10,000 Draw**() calls which is optimistically only 10x higher than any Direct3D 9 application should be generating [lol]

Quote:
1. Batch all your textures. To minimize texture changes, you need to put all your tiles onto one (or possibly several) larger textures.
Agreed, this is a definite performance advantage.

Quote:
2. Use dynamic vertex buffers to blast several thousand polies to the screen at once. For each tile you want to add, you append the geometry to the buffer and set the texture coordinates to corrospond to your batched tile. Using an index buffer is a good idea, you will use 33% less bandwidth piping geometry to the GPU.
Makes sense, but a far bigger gain in my experience is to not modify the geometry in the main loop. It's not easy to architect, but it's complication that gets you a cookie [smile]

Two optimizations I did in one of my tile-based engines was to store a CPU-side cache of the visible set (located in RAM = fast(er) CPU manipulation) and only ever updated the buffers when the camera/player moved. Because of the CPU-side cache I could throw a single chunk of vertex data (note: index data never changes) up between a lock (no processing between Lock()/Unlock() [wink]) and take full advantage of no-overwrite/discard/dynamic buffers.

Quote:
I do get really good performance: 70 FPS rendering a 100x100 tilemap
That's not bad, but I suspect you're actually clamped to a 70hz refresh rate rather than it actually being the upper performance limit.

Now, for an interesting idea... I had a "pure 3D" tile-map engine a while back that could render enough 2x2 tiles to cover a 1024x768 screen (roughly 200,000 tiles) to still clock up around 25-30hz - which is just over 7x the triangle throughput of your example [smile]

Okay, I don't wish to be cocky - but just thought it was an interesting example of what should be possible given a bit of effort.

By sticking to regular 3D geometry, that is, not POSITIONT or D3DFVF_XYZRHW and an orthogonal view you can move pretty much every piece of graphics related work to the GPU. No more resource manipulation required, hardware accelerated vertex effects (e.g. lighting and animation). The only difficult part in implementing it this way is everyones favourite texels-pixels mapping. In my example I didn't really need that so I conveniently ignored it, but it should be solveable.

Quote:
I can do 4 layers with tiles spanning two textures, using simple DrawPrimitiveUP (insert BOOs here)
* boo... hiss... *

Cheers,
Jack

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Quote:
Original post by Agony
Quote:
Original post by Evil Steve
...
Using index buffers is pointless for 2D tile engines, since each vertex is used exactly once (Due to texture coordinates being different where vertices could be shared). So you're just as well to render as much as possible (often the whole screen) in one DrawPrimitive() call.

Actually, for each quad, you can cut the number of vertices down from 6 to 4, since the two triangles that make up the quad do indeed share two vertices, texture coordinates and all. (Thus Telamon's 33% less bandwidth figure.) I'm guessing you probably knew this, but just briefly forgot about it. But for anyone else's information...
Ah, I had a mental blank there [smile]

What I meant was, if you have a grid of tiles (E.g. 30x20), then you can't share the top right vertex of the first tile with the top left vertex of the second tile for instance.
You can still render them as triangle strips, but you'd end up having to make one DrawPrimitive() call per tile, or end up using a bunch of degenerate triangles (Actually, an index buffer might help there).

Has anyone done any profiling about this? It'll probably be pretty close, performance-wise anyway...

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Now, for an interesting idea... I had a "pure 3D" tile-map engine a while back that could render enough 2x2 tiles to cover a 1024x768 screen (roughly 200,000 tiles) to still clock up around 25-30hz - which is just over 7x the triangle throughput of your example [smile]

Okay, I don't wish to be cocky - but just thought it was an interesting example of what should be possible given a bit of effort.


I suspect I am fill-rate limited, since my render target is 1200x1200 and I am on a 4 year old laptop with a Geforce 440 Go.

Quote:

I'm getting really tired of this "bring back DiriectDraw" crap. Direct3D isn't that hard, don't blame it because you couldn't research the proper way to do things. D3D can do ANYTHING DirectDraw can, some even FASTER than DirectDraw.


Yeah, but if you don't care about alpha blending, fast scaling, or rotation, D3D is overkill. My original point is that there should be no learning curve for doing something as simple as rendering a tilemap. Maybe you really like researching how 3D libs work and think the MSDN DX help files are really interesting stuff, but I just want to get on to the more interesting parts of my game.

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Original post by Pipo DeClown
Jack: that's a pretty awesome experiment! You rock! *kiss kiss*
[lol]

Quote:
I suspect I am fill-rate limited, since my render target is 1200x1200 and I am on a 4 year old laptop with a Geforce 440 Go.
Sounds reasonable - things have come a long way since the GeForce 4's [smile]

Quote:
Yeah, but if you don't care about alpha blending, fast scaling, or rotation, D3D is overkill. My original point is that there should be no learning curve for doing something as simple as rendering a tilemap.
Fair enough really... but I'd equally argue that some of the more technical aspects of DirectDraw (e.g. pixel formats and swap-chains) are also overkill. Why not just go for GDI or GDI+ or whatever drawing libraries .Net exposes? From the snippets I've seen of that, it seems even easier than DirectDraw.

But most people will avoid GDI/Win32 because of the overhead and the fact that it is very high-level. So you drop down a notch to DirectDraw and get some performance back at the cost of a bit more complexity. Then you hit the limits of DDraw (texture effects, rotation/scaling etc..) and step further down into Direct3D...

Guess you just have to pick a position on the GDI<->DDraw<->D3D slider that suits you [smile]

Cheers,
Jack

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can anybody write in breif what this post talks about :) or put lines under the important stuff coz i want to read it and at the same time i don't like to read long paragraphs

Best Regards,

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can anybody write in breif what this post talks about :) or put lines under the important stuff coz i want to read it and at the same time i don't like to read long paragraphs


Wow.

Anyway, on topic: It should be noted that OpenGL is not a good suggestion as a replacement for D3D if you are using the argument "its hard to get D3D to do simple 2D tilemaps with good performance." It's very easy to do 2D tilemaps in OpenGL via glBegin() and friends... but that will be rather slow.

Better to consider the use of a library such as SDL or Allegro (I think?) that abstracts the stuff away for you.

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Original post by jad_salloum
can anybody write in breif what this post talks about :) or put lines under the important stuff coz i want to read it and at the same time i don't like to read long paragraphs


If you really wanted to read it, you'd put some effort in. I suppose the same thing would apply for your grammatical qualities.

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Original post by jpetrie
Anyway, on topic: It should be noted that OpenGL is not a good suggestion as a replacement for D3D if you are using the argument "its hard to get D3D to do simple 2D tilemaps with good performance." It's very easy to do 2D tilemaps in OpenGL via glBegin() and friends... but that will be rather slow.

Better to consider the use of a library such as SDL or Allegro (I think?) that abstracts the stuff away for you.


thanks for u jpetrie for clearing the picture so +++ for u


Quote:

If you really wanted to read it, you'd put some effort in. I suppose the same thing would apply for your grammatical qualities.


and for u Ravuya u should have some sense of humor man and and i advice u to go make something useful in ur life and start teaching Grammer instead of fooling around. --- for u Cheeers

and 1 more thing STOP DECREASING MY RATE PEOPLE :)

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Bumping this up a bit I know but using the methods described in the first post would it be possible to texture the tiles using single indivual images or would you have to use 1 large bitmap with all the textures in that. Because I'm thinking of re-writing my Tile engine in order to use those methods.

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      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
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